This invention relates to an electrical switch, and more particularly to a rotary indexing electrical switch assembly.
An indexing rotary switch is employed in applications to control operating characteristics or parameters. In a representative application, an indexing rotary switch assembly is employed in an electrical arc welder to control current flow or other settings. A different electrical contact configuration is attained at each position of the rotary switch assembly, to set the parameters of operation.
A prior art rotary switch assembly utilizes a plastic injection molded base with a series of radially spaced contact members insert molded into the base. Each contact member defines a flat front surface which is flush with a front surface defined by the base, and a rearwardly or outwardly facing threaded passage. The base is configured such that the rearwardly or outwardly facing passage is exposed, and the lead of a cable is connected to the contact member via a threaded screw which extends into the passage. The prior art construction further involves use of a dust shield, formed separately from the base. The dust shield has a cylindrical wall which engages the outer peripheral edge of the base outwardly of the contact surfaces of the contact members. A rotary contact member is secured to and rotatable with an actuator shaft, which extends through a central opening formed in the base. In one version, a center contact is insert molded into the material of the base along with the outer contact members, and the rotary contact member establishes a connection between the center contact and one of the contact members. In another version in which the center contact is omitted, the rotary contact member selectively establishes a connection between selected pairs of the radially spaced contact members.
While the above-described construction has been found to function satisfactorily, it involves certain drawbacks in manufacture, assembly and operation. For example, insert molding of the outer contact members and the center contact is sensitive and labor intensive, in that the insert molded components must be manually placed within the mold in accurate positions since the contact positions cannot be altered after the insert molding process. This construction can lead to high rates of part rejection, since the contact positions are subject to very tight tolerances so as to ensure proper operation.
It is an object of the present invention to provide an indexing rotary contact switch having a number of design, manufacturing and operating enhancements as compared to prior art indexing rotary contact switches. It is a further object of the invention to provide such a rotary contact switch having a reduced cost of manufacture and which reduces the rate of part rejection. Yet another object of the invention is to provide such a rotary contact switch which is capable of being produced in a wide range of switch contact configurations utilizing common parts. A still further object of the invention is to provide such a switch assembly which entails use of a relatively small number of components so as to reduce manufacturing costs and increase reliability and quality. Yet another object of the invention is to provide such a rotary contact switch which eliminates insert molding of the contacts with the base. A still further object of the invention is to provide such a rotary contact switch which is relatively simple in its design and manufacture, yet which entails a number of advantages in part manufacture, assembly and overall operation.
In accordance with the invention, an indexing rotary contact switch assembly includes a base having a series of radially spaced stationary contact areas, and a rotary contact arrangement mounted for rotary movement relative to the base. The rotary contact arrangement includes at least one rotary contact area, and is movable to a plurality of contact positions in which the rotary contact area of the rotary contact arrangement engages at least one of the stationary contact areas of the base.
The base is preferably formed so as to include a series of radially spaced passages, and the stationary contact areas are defined by contact members received within certain passages in the base. The contact members are engaged within the passages according to the desired configuration of the switch assembly, so as to place the contact areas in certain locations on the base. The contact members are secured to the base after production of the base, so that the same base can be used to form a base assembly with a variety of contact configurations. In one form, the base is formed so as to define a generally circular opening, and the passages are formed in an insulating ring that is engaged within the generally circular opening. The insulating ring is configured to close the opening. In this manner, the forward portion of the base, within which the stationary contact areas and the rotary contact arrangement are located, is isolated from the environment in which the switch assembly is employed, such as within the interior of the housing of an electrical arc welder or the like. The insulating ring may be formed to have any number of openings in any desired configuration, to provide flexibility in the design and manufacture of the switch assembly.
A combination lift and detent arrangement is interposed between the base and the rotary contact arrangement. The lift and detent arrangement functions to lift the rotary contact area away from the stationary contact areas of the base upon rotation of the rotary contact arrangement between the stationary contact areas, and releasably maintains the rotary contact arrangement in a contact position in which the rotary contact area is in contact with at least one of the stationary contact areas of the base. The lift and detent arrangement preferably includes ramp structure formed integrally with the base, and at least one lift member associated with the rotary contact arrangement. The lift member engages the ramp structure upon rotation of the rotary contact arrangement to lift the rotary contact area away from the base, and engages the ramp structure when the rotary contact member is stationary so as to maintain the rotary contact arrangement in the contact position. The ramp structure may be in the form of a series of individual radially spaced ramps formed integrally with the base, and each ramp is preferably located so as to correspond in location to one of the stationary contact areas.
The switch assembly may include a center contact selectively engageable with the base and defining a stationary center contact area. The rotary contact arrangement includes a rotary inner contact area engageable with the stationary center contact area. The center contact and the base include cooperating engagement structure for engaging the center contact with the base subsequent to manufacture of the base. The center contact includes an opening through which an actuator shaft associated with the rotary contact arrangement extends. The cooperating engagement structure may be in the form of a fastener engaged between the center contact and the base on one side of the opening, in combination with a tab formed on the center contact and engageable within an opening in the base, on the opposite side of the opening.
The actuator shaft of the rotary contact arrangement includes a forward section located forwardly of the base and a rearward section located rearwardly of the base. The forward section of the actuator shaft is adapted to mount an actuator handle which is manually engageable by a user for imparting rotation to the rotary contact arrangement. A second rotary indexing switch assembly is adapted for mounting rearwardly of the base of the first-mentioned switch assembly, and the respective switch assemblies include respective first and second actuator shafts. The actuator shafts are similarly constructed, and the forward section of the second actuator shaft is adapted to be received within an opening in the rearward section of the first actuator shaft. Mating engagement structure is interposed between the first and second actuator shafts, for imparting rotation to the second actuator shaft upon rotation of the first actuator shaft. The mating engagement structure may be in the form of radially spaced axially extending splines which function to rotate the second actuator shaft upon rotation of the first actuator shaft. A positioning arrangement, such as a missing spline, may be provided for positioning the second actuator shaft in a predetermined orientation relative to the first actuator shaft.
The switch assembly further includes a conical spring arrangement interposed between the actuator shaft and the rotary contact member, for biasing the rotary contact member toward the radially spaced stationary contact areas of the base. The conical spring defines a passage through which the actuator shaft extends, and includes a first end spaced from the rotary contact member and a second end in engagement with the rotary contact member. The second end has a transverse dimension greater than the first end. A spring retaining member, such as a snap ring, is engaged with the actuator shaft for engaging the first end of the conical spring, to compress the spring and to bias the contact member toward the stationary contact areas of the base.
The base preferably has an integrally formed enclosure wall which extends from the surface of the base containing the stationary contact areas. The contact areas are contained in a contact surface defined by the base, and the enclosure wall cooperates with the contact surface to define an internal cavity within which the stationary contact areas and the rotary contact member are located. The enclosure wall is adapted to engage a planar member to which the switch assembly is mounted, such as the wall of the welder housing, for enclosing the internal cavity defined by the enclosure wall and the contact surface.
The switch assembly further includes a selectably positionable stop arrangement interposed between the rotary contact arrangement and the base for controlling the range of rotary movement of the rotary contact arrangement relative to the base. The stop arrangement includes a pair of stop members which are engageable with the base in varying locations. The actuator shaft includes an engagement member which engages the stop members upon rotation, to control the range of rotary movement of the rotary contact arrangement.
The base and the actuator shaft can be employed to mount either a first contact member or a second contact member to the rotary switch assembly. The first contact member includes a first contact arrangement adapted to engage the stationary contact areas in a first configuration, and the second contact member includes a second contact arrangement adapted to engage the stationary contact members in a second configuration. A differently configured switch assembly is attained by engaging either the first contact member or the second contact member with the actuator shaft, and rotatably mounting the selected contact member and the actuator shaft to the base.
The invention further contemplates a method of producing a base having a selectively configurable stationary contact arrangement, substantially in accordance with the foregoing summary.
The various features of the invention may be employed independently, and each is capable of improving an aspect of operation or assembly of a rotary indexing switch assembly. In a preferred form, the various aspects can be employed in combination to provide a rotary indexing switch assembly with significant advantages in assembly and operation.
Various other features, objects and advantages of the invention will be made apparent from the following description taken together with the drawings.